The invention relates to a linear drive unit comprising a first principal body having a section part, which is U-like in cross section, a second principal body, which has a housing (drive housing), said housing being placed at the U-like opening of the section part with the placement therebetween of linear guide means permitting a guided linear relative movement, and at least one drive space in the interior of the drive housing, such drive space containing components of a drive means projecting on at least one terminal side of the second principal body and engaging the associated axial terminal region of the first principal body, and on activation thereof the linear relative movement is caused between the two principal bodies.
In the case of a linear drive unit of this type disclosed in the European patent publication 0 603 459 A2 the slide-like first principal body has its U-like section part set on the top side of the drive housing of the second principal body straddling a guide rail mounted on the top side of the drive housing. In the principal body two drive spaces are formed, which each house components of a fluid operated drive means, which are connected with the one axial terminal region of the first principal body. By activation of the drive means a linear relative movement may be produced between the principle bodies, linear guide means placed between the two principal bodies serving to provide for guidance of the movement.
One disadvantage of the known linear drive unit resides in the fact that the guide play of the linear guide means is relatively difficult to adjust. As a rule such adjustment is performed by resetting the position of the components, running of the section part of the first principal body, in relation to the principal body. On the one hand this means having suitable adjustment means, something which increases the costs of production of the linear drive unit. On the other hand the adjustment is relatively complex, because the linear guide means are covered over by the U-like section part of the first principal body and therefore are only to be accessed or seen with difficulty.
One object of the present invention is to provide a linear drive unit, which despite having an economic price is simple and exact as regards adjustment.
In order to achieve this aim there is a provision such that the section part of the first principal body straddles the drive housing of the second principal body so that its longitudinal limbs flank the lateral side faces of the drive housing, the linear guide means being arranged between each limb of the section part and the facing lateral face of the drive housing, and that the section part comprises two section elements which respectively comprise one of the limbs and are firmly fitted together so as to set the guide play of the linear drive means alongside each other.
Accordingly a linear drive unit is provided, in the case of which during assembly of the U-like section part the guide play of the linear guide means can be simultaneously automatically set so that later complex adjustment work is unnecessary and it is possible to use inexpensive linear guide means, which for their part do not have any special play adjustment means. The limbs, which flank the drive housing, of the U-like section part are components of originally separate section elements, which during assembly of the linear drive unit are placed alongside each other, so that initially they are freely movable and slidable in relation to each other and the width of the intermediate space between their limbs may be varied and set by predetermining different relative positions. Since the set width of the intermediate space directly influences the guide play of the linear guide means placed between each respective limb and the drive housing, it is therefore possible to preset the desired guide play by the selected positioning and biasing effect very simply. By then firmly joining together the section elements, as for instance by bonding, the setting produced will be permanently maintained so that later adjustment will not be necessary. More particularly in the case of linear drive units with small and miniature dimensions the product design in accordance with the invention exhibits unique advantages, because in this case formerly owing to the miniaturized structure manipulations could only be performed in an extremely awkward manner if at all.
Further advantageous developments of the invention are defined in the dependent claims.
The linear guide means are preferably designed in the form of rolling element guides and possess guideways provided on each limb of the section part and on the facing lateral faces of the drive housing, such guideways cooperating with intermediately placed rolling elements. The latter can in this case be grouped together as rolling element units.
The section elements constituting the section part are preferably L-like in cross section and so put together that they overlap at pairs of their L-like limbs. In the overlap part it is possible for the L-like limbs to be bonded together or joined together in some other fashion.
In the case of a particularly advantageous design the drive housing is provided with two juxtaposed drive spaces for each on drive unit, the two drive units being able to engage at the same axial end region or at two opposite end regions of the first principal body. The last named design is more particularly to be employed in connection with a first principal body which is long in relation to the overall length of the second principal body, the second principal body being overlapped at both oppositely facing terminal faces by the first principal body.
The drive units may be so designed that each of them is responsible for the production of the linear relative movement in only one of the two possible directions of motion. It is particularly advantageous for this to be in conjunction with a design of the drive means in a fluid operated system, since here the number of seals is substantially reduced.
Each respective drive means has, in the case of a fluid operated design, preferably a piston which is arranged in a sliding manner in an associated working space in the drive housing, said piston engaging the respective terminal axial end region of the first principal body by way of a force or power transmitting part, which extends longitudinally. In this case the power transmitting part may be annular in design and, in order to favor simple production, constitutes a sort of plunger piston together with the piston.
In the case of a component unit designed in a hollow form there is the possibility of accommodating an abutment unit in the interior of the piston and/or of the force transmitting part, said unit being able to be used to set the terminal position of the piston and accordingly of the relative movement produced by it. The abutment unit will conveniently have a variably positionable abutment part in order to set different terminal positions of the piston as may be required.
Resetting the terminal position of the piston is preferably performed through an opening provided at the end of the force transmitting part opposite to the piston, such opening permitting the introduction of a suitable setting tool.
The abutment unit may be provided with a buffer and/or damping means in order to reduce the terminal impact.
It is convenient for the respective-drive means to engage the respective axial terminal region of the first principal body by the intermediary of a transverse part, such transverse part extending in the intermediate space between the two limbs of the section part and preferably being anchored also on both limbs. This transverse part may more particularly be plate-like and be so aligned that the plane of its plate is perpendicular to the longitudinal axis of the first principal body.
It is more especially advantageous for the transverse part to so interlock with the two limbs that between it and the section part play-free force transmission is possible, and at least a small degree of play permitting movement being present between the transverse part and the limbs in the transverse direction, such play existing simultaneously on assembly of the section elements and/or on permanent fitting together of same. This means that there is a play-free transmission of the drive forces, there at the same time being an exact, aligned arranged of all components, something which prevents excessive wear. It is possible to have such a provision that the transverse part is floatingly mounted on the section part athwart the latter, either by leaving a certain space for play or by integration of elastically yielding compensation means.
In the following the invention will be described in detail with reference to the accompanying drawings.